Three phase immiscible polymer-metal blends for high conductivty composites

ABSTRACT

Provided is a method of forming a conductive polymer composite. The method includes forming a mixture. The mixture includes a first thermoplastic polymer, a second thermoplastic polymer and a plurality of metal particles. The first thermoplastic polymer and the second thermoplastic polymer are immiscible with each other. The plurality of metal particles include at least one metal that is immiscible with both the first thermoplastic polymer and the second thermoplastic polymer. The method includes heating the mixture to a temperature greater than or equal to a melting point of the metal.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 14/948,070filed Nov. 20, 2015 (allowed), the entire disclosure of which is herebyincorporated herein by reference in its entirety.

DETAILED DESCRIPTION Field of the Disclosure

The present disclosure is directed to three-phase immisciblepolymer-metal blends for high conductivity composites.

Background

Additive manufacturing (also known as three dimensional printing) aspracticed in industry has been, to date, mostly concerned with printingstructural features. There is a need for materials and processes thatintegrate functional properties (such as electronic features) intoadditive manufacturing. Recently, conductive materials that arepotentially useful in additive manufacturing have been commercialized,but their conductivities are generally low, ranging from ˜10⁻³ S/cm toupwards of ˜2.0 S/cm. The mechanical properties of the commerciallyavailable materials, particularly the conductive materials such asAcrylonitrile butadiene styrene (ABS) or polylactic acid (PLA), aregenerally limited (e.g., are not flexible, are fairly brittle) and havelimited use as a conductive component.

There is great interest in the field of additive manufacturing todevelop improved materials that can be used to easily print completelyintegrated functional objects with limited post-assembly. This wouldallow completely new designs in the manufacturing and consumption ofeveryday objects, particularly when they can be enabled with conductivematerials. The capability of printing conductive components within anobject can provide the potential for embedded sensors and electronics.

Common techniques in additive manufacturing utilize the extrusion ofmolten polymer through a heated nozzle. This method is used in, forexample, fused deposition modeling (FDM), where a filament is fed into ahot zone for continuous extrusion. The molten polymer can be depositedlayer by layer onto a build plate in order to form 3D objects. There arevery few filament materials currently on the market which exhibitelectrical conductivity, and those which are available have relativelylow conductivities, which limits the range of potential applications.The materials are typically constructed such that one conductivematerial forms a percolating network through an insulating polymer base,such that electrons have a continuous pathway to flow. The formation ofthis conductive network is limited to the way the conductive particlesare arranged within the polymer base. Although these materials have beenextensively explored in both academia and industry, the focus istypically on minimizing the amount of conductive additive required toform a percolating network, where the conductivity is relatively low.One example of a paper directed to the study of dispersion of carbonblack in an immiscible polymer blend is Feng, J. et al., A Method toControl the Dispersion of Carbon Black in an Immiscible Polymer Blend,Polymer Engineering & Science 2003, 43(5), 1058-1063, which describesthat the dispersion of carbon black in an immiscible polymer blend isstrongly influenced by the viscosity of one of the polymers of thepolymer blend. This paper does not describe techniques for increasingconductivity substantially beyond the percolation threshold. Nor does itdiscuss the use of conductive polymers for additive manufacturing. Oneexample of a patent directed to a conductive polymer is U.S. Pat. No.6,331,586 by Thielen, A. et al. and published on Dec. 18, 2001, whichdescribes a conductive polymer blend which is comprised of twoimmiscible polymers and a conductive material in particulate or fiberform. The patent does not describe techniques for increasingconductivity substantially beyond the percolation threshold.

Novel plastic composite materials that exhibit increased conductivitywould be a welcome step forward in the art, and could have significantimpacts in the field of additive manufacturing.

SUMMARY

An embodiment of the present disclosure is directed to a method offorming a conductive polymer composite, comprising: forming a mixturecomprising a first thermoplastic polymer, a second thermoplastic polymerand a plurality of metal particles, wherein the first thermoplasticpolymer and the second thermoplastic polymer are immiscible with eachother, and wherein the plurality of metal particles comprise at leastone metal that is immiscible with both the first thermoplastic polymerand the second thermoplastic polymer; and heating the mixture to atemperature greater than or equal to a melting point of the metal.

In another embodiment, there is a conductive polymer composite,comprising: a first thermoplastic polymer; a second thermoplasticpolymer; and plurality of metal particles, wherein the firstthermoplastic polymer and the second thermoplastic polymer areimmiscible with each other, and wherein the plurality of metal particlescomprise at least one metal that is immiscible with both the firstthermoplastic polymer and the second thermoplastic polymer.

In another embodiment, there is a polymer composite filament,comprising: a first thermoplastic polymer defining a first continuousdomain; a second thermoplastic polymer defining a second continuousdomain, wherein the second thermoplastic is immiscible with the firstthermoplastic; and a continuous metal trace disposed at an interface ofthe first continuous phase and the second continuous phase.

The compositions of the present application exhibit one or more of thefollowing advantages: improved conductivity of filaments for 3D printingapplications, such as fused deposition modeling (FDM); an unexpected, aphase separation of an alloy at its melting point which can be utilizedin a two-phase immiscible polymer system to form a continuous conductivetrace; or an improved method for increasing the electrical conductivityin composites while retaining material properties suitable for additivemanufacturing.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the present teachings, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrates embodiments of the presentteachings and together with the description, serve to explain theprinciples of the present teachings.

FIG. 1 is a flowchart showing the steps of a method of an embodiment.

FIG. 2 is a photograph showing an example of BiSnAg alloy phaseseparation in poly(styrene-isoprene-styrene) block copolymer to thesurface of a filament during extrusion.

FIGS. 3A-3B are scanning electron micrographs of a filament comprisingBiSnAg particles in polycaprolactone extruded below the melting point ofBiSnAg (FIG. 3A), and above the melting point of BiSnAg and showing thephase separation and coalescence into larger domains (FIG. 3B).

It should be noted that some details of the figure have been simplifiedand are drawn to facilitate understanding of the embodiments rather thanto maintain strict structural accuracy, detail, and scale.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to embodiments of the presentteachings, examples of which are illustrated in the accompanyingdrawings. In the drawings, like reference numerals have been usedthroughout to designate identical elements. In the followingdescription, reference is made to the accompanying drawing that forms apart thereof, and in which is shown by way of illustration a specificexemplary embodiment in which the present teachings may be practiced.The following description is, therefore, merely exemplary.

An embodiment of the present disclosure is directed to a conductivepolymer composite. Generally, the conductive composite materialcomprises three immiscible phases which provide for the formation of acontinuous conductive domain to be formed from one of the immisciblephases. That is, the composite comprises a three-phase compositematerial which contains a continuous metal trace, allowing for higherconductivity applications in additive manufacturing. The three-phasecomposite material comprises at least three components: firstthermoplastic polymer, a second thermoplastic polymer, and a metal.These components are immiscible in order to form the three co-continuousdomains. These domains can be formed at any point during processing:melt mixing, extrusion into filament, or extrusion during 3D printing.

The composites of the embodiments and methods of making such compositesas described herein offer significant improvement over current compositematerials. For example, as a result of the first thermoplastic polymerand the second thermoplastic polymer being immiscible with one another,melt-mixing the first thermoplastic polymer, the second thermoplasticpolymer and the metal at a temperature below the melting point of themetal causes the metal to localize at an interface of the twoco-continuous phases of the immiscible first and second thermoplasticpolymers. After localization, the melt-mix can be heated above themelting point of the metal in order to form a larger, continuous domain.Alternatively, all three of the first thermoplastic polymer, the secondthermoplastic polymer and the metal can be processed above the meltingpoint of the metal to form three immiscible phases, each of which formsa co-continuous domain with the other. As a result of either of theseprocesses, the conductivity of filaments formed by extrusion of suchmelt-mixtures does not depends on the metal/conductor forming apercolation network between particles thereof. Instead, for theembodiments described herein, the conductivity of the conductivecomposite filaments, for example, as measured between two ends thereof,comprises the conductivity of the metal itself, which is orders ofmagnitude higher than what's typically achieved in a percolatingnetwork. Accordingly, the embodiments described herein provide forconductive polymer composites to comprise any metals having low-meltingtemperature, including alloys and nanoparticles.

As shown in FIG. 1, in an embodiment a method 100 for forming aconductive polymer composite comprises forming a mixture at 101. Themixture can include a first thermoplastic polymer 11, a secondthermoplastic polymer 13 and a plurality of metal particles 15. Thefirst thermoplastic polymer and the second thermoplastic polymer may beselected such that they are immiscible with each other. The plurality ofmetal particles may comprise at least one metal that is immiscible withboth the first thermoplastic polymer and the second thermoplasticpolymer. The method continues with heating the mixture at 103, forexample, to a temperature greater than or equal to a melting point ofthe metal. In an embodiment, upon heating the mixture, the plurality ofmetal particles undergo a phase separation comprising coalescing of atleast two of the plurality of metal particles. While not limited to anyparticular theory it is believed that the plurality of metal particlespreferentially localize at an interface between the first thermoplasticpolymer and the second thermoplastic polymer. Such an interface may bethe result of an interfacial tension between two co-continuous polymerphases forming a boundary where the particles preferentially localize asa result of a predetermined ratio of viscosities between the first andsecond thermoplastic polymers.

The mixture of the first thermoplastic polymer, the second thermoplasticpolymer and the plurality of metal particles can be formed by meltingthe first thermoplastic polymer and the second thermoplastic polymersuch that they form two co-continuous immiscible phases separated by aninterface. Accordingly, melting can include melting the firstthermoplastic polymer and the second thermoplastic polymer at atemperature below the melting point of the at least one metal. As aresult, the mixture can, therefore, include a first domain that includesfirst thermoplastic polymer, a second domain that includes the secondthermoplastic polymer, and a third domain that includes the metal. In anembodiment, mixing may include melt-mixing the first thermoplasticpolymer and the second thermoplastic polymer. In an embodiment, themethod 100 can include extruding the mixture at 105 and forming aconductive polymer composite filament at 107.

The method can further include forming a composite by cooling the heatedmixture, wherein the composite comprises a continuous metal trace. Themethod can further include providing the composite to athree-dimensional-printer, heating the composite, and extruding theheated composite onto a substrate to form a three-dimensional object. Inan embodiment, the mixing step can include providing the firstthermoplastic polymer, the second thermoplastic polymer and the metal toa three-dimensional printer followed by melting the first thermoplasticpolymer and the second thermoplastic polymer and extruding the heatedmixture onto a substrate to form a three-dimensional object.

Thermoplastic Polymers

Any suitable thermoplastic polymer useful in three-dimensional printingcan be employed as the first and the second thermoplastic polymers inthe composites of the present disclosure. In an example, the first andsecond thermoplastic polymers are immiscible with each other.Accordingly, the first thermoplastic polymer may be different than thesecond thermoplastic polymer. While not limited to any particulartheory, it is believed that hydrophobic/hydrophilic characteristic of athermoplastic polymer is a physical property that provides for theimmiscibility between different thermoplastic polymers. Accordingly, inan embodiment, the first thermoplastic polymer is more hydrophobic thanthe second thermoplastic polymer. Alternatively, in an embodiment, thesecond thermoplastic polymer is more hydrophobic than the firstthermoplastic polymer. Meanwhile, in an embodiment, the firstthermoplastic polymer is more hydrophilic than the second thermoplasticpolymer. Alternatively, in an embodiment, the second thermoplastic ismore hydrophilic than the first thermoplastic polymer. In anotherembodiment, the first thermoplastic polymer is hydrophobic and thesecond thermoplastic polymer is hydrophilic. Alternatively, in anembodiment, the second thermoplastic polymer is hydrophobic and thefirst thermoplastic polymer is hydrophilic.

The first and the second thermoplastic polymer may be selected from highdensity polyethylene (HDPE), metallocene catalyzed linear low densitypolyethylene (mLLDPE), polypropylene (PP) thermoplastic urethane (TPU),ethylene propylene rubber (EPR), ethylene propylene diene rubber (EPDM),Poly(styrene-isoprene-styrene), polycaprolactone, acrylonitrilebutadiene styrene (ABS), polylactic acid (PLA), copolymers thereof suchas block copolymers thereof, or any combinations thereof.

Exemplary combinations of first and second thermoplastic polymer (e.g.,first theremoplastic polymer/second theremoplastic polymer) include:HDPE/EPR, HDPE/EPDM, HDPE/mLLDPE, PP/EPDM, PP/EPR, PP/mLLDPE, andmLLDPE/EPR.

The amounts of the first and second thermoplastic polymer may beselected such that the first and second thermoplastic polymers formco-continuous domains when mixed together. In an example, the polymericcontent of a composite of the embodiments can be selected such that thefirst thermoplastic polymer comprises from about 10% to about 90% byweight relative to the total weight of the conductive polymer composite,and the second thermoplastic polymer comprises from about 10% to about90% by weight relative to the total weight of the conductive polymercomposite. In an example, the polymeric content of a composite of theembodiments can be selected such that the first thermoplastic polymercomprises from about 2.5% to about 67.5% by weight relative to the totalweight of the conductive polymer composite, for example 5% to about67.5% by weight relative to the total weight of the conductive polymercomposite; and the second thermoplastic polymer comprises from about2.5% to about 67.5% by weight relative to the total weight of theconductive polymer composite, for example, from about 5% to about 67.5%by weight relative to the total weight of the conductive polymercomposite.

The composite can include three immiscible components. The componentsmay include two polymers (i.e., the first thermoplastic polymer and thesecond thermoplastic polymer and one metal or metal alloy. In otherwords, the composite can comprise a first thermoplastic polymer, asecond thermoplastic polymer and at least one metal.

Metal

For the metal, any suitable metal useful in three-dimensional printingcan be employed in the composites of the present disclosure. The metalmay be selected from any metal and may include metal alloys. Anysuitable metal can be employed, for example, in particular form.Examples of suitable metals include Bi, Sn, Sb, Pb, Ag, In, Cu, oralloys thereof. For example, alloys may include at least one of thefollowing, BiSnPb, BiSn, BiSnAg, SbPbBi, SnBi, InSn, SnInAg, SnAgCu,SnAg, SnCu, SnSb, SnAgSb, or mixtures thereof.

The metal may be selected based on its melting temperature, for example,in ambient environments. For example, metals comprising a meltingtemperature (Tm) in the range of from about 100° C. to about 250° C. maybe selected. The metal may be immiscible with the first thermoplasticpolymer and the second thermoplastic polymer.

Example amounts of metal include a range of from 10% to about 75% byweight, such as from about 25% to about 75% by weight, or from about 50%to about 75% by weight relative to the total weight of the conductivepolymer composite.

The conductive polymer composites of the present disclosure can includeany other suitable ingredients in any desired amounts, although notrequired. Alternatively, ingredients not expressly recited in thepresent disclosure can be limited and/or excluded from the conductivepolymer composites disclosed herein. Thus, the amounts of thethermoplastic polymer, metal, first polymer and second polymer asrecited herein, can add up to from about 90% to about 100% by weight ofthe total ingredients employed in the composites of the presentdisclosure, such as from about 95% to about 100% by weight, or fromabout 98% to about 100% by weight, or from about 99% to about 100% byweight, or about 100% by weight of the total ingredients.

Because of the continuous metal domains that form at an interfacebetween immiscible thermoplastic polymers, the composite of theembodiments also has a bulk conductivity of the bulk metal of theselected metal. Bulk conductivity is calculated using the formula,

σ=L/(R*A)  (1)

Where:

-   -   σ is bulk electrical conductivity;    -   L is length of the filament;    -   R is measured resistance of an extruded filament;    -   A is the cross-sectional area (πr²) of the filament, where r is    -   the radius of the filament.        The resistance, R, can be measured by forming an extruded        filament made from the composite. The tips of the filament are        painted with silver to provide good electrical connections with        the testing equipment (e.g., a digital multimeter), but would        not necessarily be painted if the filaments were to be used in        additive manufacturing. Resistance can then be measured across        the length of the filament. The dimensions of the filament and        the measured value for R can then be used to calculate bulk        conductivity (a) of the composite.

The composites of the present disclosure can be made by any suitablemethod. For example, the thermoplastic polymer can be combined with thefirst polymer, the second polymer and the metal particles using meltmixing techniques. Other suitable techniques for mixing suchcompositions are well known in the art.

The present disclosure is also directed to a method of three dimensionalprinting. The method includes providing any of the conductive polymercomposites of the present disclosure to a three dimensional printer. Thecomposite can be in any suitable form useful in three dimensionalprinting, such as a filament. The conductive polymer is generally heatedto a molten state suitable for extrusion. Then the heated conductivepolymer is extruded onto a substrate to form a three dimensional object.

EXAMPLES Example 1

Poly(styrene-isoprene-styrene) block copolymer was melt mixed withBiSnAg metal alloy (Indalloy #282, available from INDIUM CORPORATION®,United States) for 30 minutes at 30 rpm in a twin screw extruder.Filaments were extruded on a melt flow indexer to form filaments 1.75 mmin diameter with a custom designed die and 19.66 kg weight. Duringprocessing, the metal alloy phase separated to areas of lower surfacetension. While melt mixing above the melting point of BiSnAg alloy onthe twin screw extruder, the alloy phase separated to the edges of thechamber. When melt mixed below the melting point of the metal alloy andextruded above the melting temperature, filament extruded from the meltflow indexer was observed as having phase separated alloy on the surfaceof the filament as shown in FIG. 2.

In addition to phase separation, the alloy particles were unexpectedlyobserved to have undergone a phase change as evidenced by larger domainsshown between FIGS. 3A-3B. While not limited to any particularembodiment, it is believed that the alloy phase separated to areas oflower surface tension.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the disclosure are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements. Moreover, all ranges disclosed hereinare to be understood to encompass any and all sub-ranges subsumedtherein.

While the present teachings have been illustrated with respect to one ormore implementations, alterations and/or modifications can be made tothe illustrated examples without departing from the spirit and scope ofthe appended claims. In addition, while a particular feature of thepresent teachings may have been disclosed with respect to only one ofseveral implementations, such feature may be combined with one or moreother features of the other implementations as may be desired andadvantageous for any given or particular function. Furthermore, to theextent that the terms “including,” “includes,” “having,” “has,” “with,”or variants thereof are used in either the detailed description and theclaims, such terms are intended to be inclusive in a manner similar tothe term “comprising.” Further, in the discussion and claims herein, theterm “about” indicates that the value listed may be somewhat altered, aslong as the alteration does not result in nonconformance of the processor structure to the illustrated embodiment. Finally, “exemplary”indicates the description is used as an example, rather than implyingthat it is an ideal.

It will be appreciated that variants of the above-disclosed and otherfeatures and functions, or alternatives thereof, may be combined intomany other different systems or applications. Various presentlyunforeseen or unanticipated alternatives, modifications, variations, orimprovements therein may be subsequently made by those skilled in theart which are also intended to be encompasses by the following claims.

What is claimed is:
 1. A conductive polymer composite, comprising: afirst thermoplastic polymer; a second thermoplastic polymer; and aplurality of metal particles, wherein the first thermoplastic polymerand the second thermoplastic polymer are immiscible with each other, andwherein the plurality of metal particles comprises at least one metalthat is immiscible with both the first thermoplastic polymer and thesecond thermoplastic polymer.
 2. The conductive polymer composite ofclaim 1, wherein the first thermoplastic polymer, the secondthermoplastic polymer, or both comprise a thermoplastic polymer selectedfrom a high density polyethylene (HDPE), metallocene catalyzed linearlow density polyethylene (mLLDPE), polypropylene (PP) thermoplasticurethane (TPU), ethylene propylene rubber (EPR), ethylene propylenediene rubber (EPDM), polycaprolactone, acrylonitrile butadiene styrene(ABS), polylactic acid (PLA), copolymers thereof, or mixtures thereof,and wherein the first thermoplastic polymer comprises a thermoplasticpolymer different from that of the second thermoplastic polymer.
 3. Theconductive polymer composite of claim 1, wherein the metal particlescomprise BiSnPb, BiSn, BiSnAg, SbPbBi, SnBi, InSn, SnInAg, SnAgCu, SnAg,SnCu, SnSb, SnAgSb, or mixtures thereof.
 4. The conductive polymercomposite of claim 1, wherein the plurality of metal particles compriseBi, Sn, Sb, Pb, Ag, In, Cu, or alloys thereof.
 5. The conductive polymercomposite of claim 1, wherein the metal particles comprise BiSnAg and atleast one of BiSnPb, BiSn, SbPbBi, SnBi, InSn, SnInAg, SnAgCu, SnAg,SnCu, SnSb, SnAgSb or mixtures thereof.
 6. The conductive polymercomposite of claim 1, wherein the composite is formed by a methodcomprising the steps of: forming a mixture comprising the firstthermoplastic polymer, the second thermoplastic polymer and theplurality of metal particles, wherein the forming the mixture comprisesmelting the first thermoplastic polymer and the second thermoplasticpolymer such that they form two co-continuous immiscible phasesseparated by an interface, wherein the melting comprises melting thefirst thermoplastic polymer and the second thermoplastic polymer at atemperature below the melting point of the plurality of metal particles;heating the mixture to a temperature greater than or equal to a meltingpoint of the plurality of metal particles; and forming the composite bycooling the heated mixture, wherein the composite comprises a continuousmetal trace.
 7. The conductive polymer composite of claim 1, wherein thefirst thermoplastic polymer comprises one or more of polycaprolactonepolylactic acid (PLA), copolymers thereof, or mixtures thereof.
 8. Theconductive polymer composite of claim 1, wherein the plurality of metalparticles is localized at an interface between the first thermoplasticpolymer and the second thermoplastic polymer.
 9. The conductive polymercomposite of claim 1, wherein at least two of the plurality of metalparticles are coalesced.
 10. The conductive polymer composite of claim1, wherein the first thermoplastic polymer defines a first continuousdomain; the second thermoplastic polymer defines a second continuousdomain; and a continuous metal trace is disposed at an interface of thefirst continuous domain and the second continuous domain.
 11. Theconductive polymer composite of claim 1, wherein the first thermoplasticpolymer comprises a poly(styrene-isoprene-styrene) block copolymer. 12.A polymer composite filament, comprising: a first thermoplastic polymerdefining a first continuous domain; and a second thermoplastic polymerdefining a second continuous domain, wherein the second thermoplasticpolymer is immiscible with the first thermoplastic polymer; and whereina continuous metal trace is disposed at an interface of the firstcontinuous domain and the second continuous domain.
 13. The polymercomposite filament of claim 12, wherein the first thermoplastic polymercomprises a poly(styrene-isoprene-styrene) block copolymer.
 14. Thepolymer composite filament of claim 12, wherein the plurality of metalparticles comprise a mixture of more than one of BiSnPb, BiSn, BiSnAg,SbPbBi, SnBi, InSn, SnInAg, SnAgCu, SnAg, SnCu, SnSb, SnAgSb.
 15. Thepolymer composite filament of claim 12, wherein the plurality of metalparticles comprises BiSnAg.
 16. The polymer composite filament of claim12, wherein the plurality of metal particles comprises BiSnAg and atleast one of BiSnPb, BiSn, SbPbBi, SnBi, InSn, SnInAg, SnAgCu, SnAg,SnCu, SnSb, SnAgSb or mixtures thereof.
 17. The polymer compositefilament of claim 12, wherein the composite is formed by a methodcomprising the steps of: forming a mixture comprising the firstthermoplastic polymer, the second thermoplastic polymer and theplurality of metal particles, wherein the forming of the mixturecomprises melting the first thermoplastic polymer and the secondthermoplastic polymer such that they form two co-continuous immisciblephases separated by an interface, and wherein the melting comprisesmelting the first thermoplastic polymer and the second thermoplasticpolymer at a temperature below the melting point of the plurality ofmetal particles; heating the mixture to a temperature greater than orequal to a melting point of the plurality of metal particles, andforming the composite by cooling the heated mixture; and wherein thecomposite comprises a continuous metal trace.
 18. The polymer compositefilament of claim 12, wherein the first thermoplastic polymer comprisesone or more polycaprolactone polylactic acid (PLA), copolymers thereof,or mixtures thereof.
 19. The polymer composite filament of claim 12,wherein the plurality of metals comprises Bi, Sn, Sb, Pb, Ag, In, Cu, oralloys thereof.
 20. A conductive polymer composite, comprising: a firstthermoplastic polymer; a second thermoplastic polymer; and a pluralityof metal particles, wherein the first thermoplastic polymer and thesecond thermoplastic polymer are immiscible with each other, wherein theplurality of metal particles comprise at least one metal that isimmiscible with both the first thermoplastic polymer and the secondthermoplastic polymer, wherein the first thermoplastic polymer defines afirst continuous domain; the second thermoplastic polymer defines asecond continuous domain; wherein a continuous metal trace is disposedat an interface of the first continuous domain and the second continuousdomain and wherein the plurality of metal particles comprises BiSnAg andat least one of BiSnPb, BiSn, SbPbBi, SnBi, InSn, SnInAg, SnAgCu, SnAg,SnCu, SnSb, SnAgSb or mixtures thereof.